All Java components require names. Names used for classes, variables and methods are called identifiers. In Java, there are several points to remember about identifiers. They are as follows -All identifiers should begin with a letter (A to Z or a to z), currency character ($) or an underscore (_). After the first character, identifiers can have any combination of characters.A keyword cannot be used as an identifier. Most importantly, identifiers are case sensitive. Examples of legal identifiers: age, $salary, _value, __1_value. Examples of illegal identifiers: 123abc, -salary.

Following books are on top from popularity and content wise and are a good resource to learn java programming from beginner to advance level.

There are many sites which are a good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava  documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/

There are many sites which are a good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/

There are many sites which are a good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint - www.Tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/

There are many sites which are a good resource to learn java. Following is the list of most popular websites.Tutorialspoint - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/

There are many sites which are good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint www.tutorialspoint.comStackOverflow www.stackoverflow.comDZone www.dzone.comWikipedia www.wikipedia.orgIBM Developer Works www.ibm.com/developerworks/java/TechGig www.techgig.comGitHub www.github.comJava documentation docs.oracle.com/javase/Coursera www.coursera.org/JavaWorld www.javaworld.com/

There are many sites which are a good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/

There are many sites which are a good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint  - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/

There are many sites which are a good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/